The present invention is in the technical field of signal processing. More particularly, the present invention is in the technical field of electromagnetic signal processing. More particularly, the present invention is in the technical field of unintended electromagnetic signal processing for the purposes of detecting, identifying and locating electronic devices.
Any electronic device necessarily emits electromagnetic radiation unintentionally. These emissions are commonly referred to as Electromagnetic Interference in other contexts and are formed by internal device signals which radiate from wires and traces which act as antenna elements. Although weak by communications standards, these radiated signals are unique, consistent and specific to a given device. A sensitive receiver, modern signal processing and a priori knowledge of the device's radiated emissions together provide a mechanism to remotely detect and identify the device. Given a database of electronic device emission structures, it is possible to monitor, detect and identify an assortment of electronic devices.
The ability to detect and identify electronic devices provides useful applications to both military and commercial applications. For example, electronically triggered improvised explosive devices may be detected through the remote reception and analysis of electronic trigger's unintended emissions. This application alone is sufficient to motivate the development of an unintended emissions sensor. However, the growing pervasiveness of electronics in modern society amplifies these interests, offering a rich diversity of applications to which device detection and identification applies, including security, tracking, and surveillance.
A previous patent application Ser. No. 12/422,646 filed Apr. 13, 2009 “ACTIVE IMPROVISED EXPLOSIVE DEVICE (IED) ELECTRONIC SIGNATURE DETECTION” which is herein incorporated by reference, addressed methodologies to amplify and distinguish these unintentional emissions through active stimulation of devices from an illumination source followed by reception of the stimulated emissions. A later patent application Ser. No. 12/551,635 filed Sep. 1, 2009 “ADVANCE MANUFACTURING MONITORING AND DIAGNOSTIC TOOL” which is herein incorporated by reference, addressed the use of unintended emissions to monitor, verify and predict the health of electronics. Another issued U.S. Pat. No. 7,515,094 Issued Apr. 7, 2009 “ADVANCED ELECTROMAGNETIC LOCATION OF ELECTRONIC EQUIPMENT” which is herein incorporated by reference, addresses additional related methods and devices.
However, the ability to detect these emissions and positively associate them with a device in the presence of a noisy electromagnetic background is particularly difficult. Received spectral content which is particular to a device must be distinguished from other received signals. Even when this is achievable, there often remains doubt as to whether the received emissions are in fact related to the targeted device. In particular, it is difficult to identify a device with a low false alarm rate when in the presence of multiple interferers, or when multiple devices are present. Further, it is difficult to dissociate identical devices from one another such that accurate geo-location may be performed.